Volumetric metering device for the metered delivery of granular and powdery materials particulary for machines for distributing such materials

ABSTRACT

A volumetric metering device for the metered delivery of granular and powdery materials, particularly for machines for distributing such materials. The device comprises a housing formed in one piece of plastic material, a metering member which is supported rotatably in the housing, can be handled individually, and includes a plurality of metering wheels mounted on a shaft and clamped in a group between two flanges, a selective drive-transmission interposed between the wheels and the shaft, a scraper for cleaning the wheels in motion and anchoring the idle wheels, and a feeler device which is held at a distance from the metering member with resilient preloading.

TECHNICAL FIELD

The subject of the present invention is a metering device for themetered delivery of granular and powdery materials, particularly formachines for distributing such materials.

TECHNOLOGICAL BACKGROUND

Volumetric metering devices are used widely in many different technicalfields in which there is a need to deliver a substantially continuousand measured flow of material over time. For example, the technicalfield of agricultural sowing machines with pneumatic seed-transportationis typical; in these machines it is known to provide a seed-loadinghopper at the base of which a metering device, generally of thevolumetric type with blades, is fitted and supplies metered quantitiesof seeds into a Venturi duct by which the seeds are admitted to anair-flow and transported to the sowing drills.

The particular and preferred application of the invention is in allcases in which it is necessary to vary the flow-rate delivered, possiblywithin a fairly large range of values.

Typical metering devices formed in accordance with the prior art aredescribed, for example, in EP 0702890, EP 0606541, EP 0471155, and U.S.Pat. No. 6,138,591.

Conventional metering devices normally comprise a box-like structure inwhich a bladed metering member is supported rotatably and cooperateswith a flow-restricting device for regulating the flow-rate delivered.In one example, the restricting device comprises a jacket movableaxially in an adjustable manner relative to the rotor of the distributorso as to cover a portion of the set of blades in order to reduce theoverall capacity of the cells available. Alternatively, the rate ofrotation of the metering member may be varied, or the capacity of thecells may be varied.

A first problem resulting from the known structure of conventionaldistributors is that they do not permit large adjustments of flow-ratewhilst maintaining constant regulation of the metering for eachadjustment. In fact, there are critical speeds of the metering memberbeyond which its reliability is reduced.

A second problem typical of known structures is that they comprise aplurality of parts which have to be assembled using connections, screws,flanges, etc. This construction is rather unsuitable for agriculturalmachines for which many adjustments have to be performed in the fieldand the consequent need to remove various parts may lead to their loss,making re-assembly impossible.

A further problem characteristic of conventional metering devices isthat they are subject to irremediable damage, or at least to blockage ofthe metering member, when foreign bodies of considerable size reach therotor. In the absence of a timely indication of this situation,particularly during sowing, it is possible, completely unwittingly, tosow whole fields unevenly or not at all.

An object of the present invention is to provide an improved volumetricmetering device that solves one or more of the problems identifiedabove.

SUMMARY OF THE INVENTION

These problems and yet others which will become clearer from thefollowing description are addressed and solved by the subject invention.In one embodiment, the invention is a volumetric metering device for themetered delivery of granular and powdery materials, particularly formachines for distributing such materials, comprising a housing and ametering member supported rotatably in the housing, characterized inthat the housing is formed in a single piece. In another embodiment, themetering member comprises at least one metering wheel clamped between apair of flanges, the housing comprising juxtaposed openings at least oneof which has dimensions such as to allow the metering member, completewith the at least one wheel and the flanges, to pass from and towardsthe housing, at least one of the flanges being arranged to close therespective opening when the metering member is fitted in the operativeposition in the housing, and constituting a mechanism for the rotatablesupport of the metering member in the housing.

In another embodiment, the metering member includes a plurality ofmetering wheels which are structurally independent of one another andare interposed in a group between a pair of flanges, and a shaft actingas a tie between the flanges in order to clamp in a group the flangesand the metering wheels interposed between them, to constitute a unitwhich can be handled individually. In yet another embodiment of thepresent invention, the metering member carries a plurality of meteringwheels having blades and being clamped together in a group,characterized in that the blades have appendages restraining the bladesof one wheel on the blades of the adjacent wheel.

The metering member of a further embodiment of the present invention hasmetering wheels clamped in a group and keyed to a commondrive-transmission shaft. A selective drive-transmission mechanism isinterposed between the wheels and the shaft in order to exclude thewheels from driving by the shaft or, conversely, to connect the wheelsfor driving by the shaft.

Pursuant to another embodiment, the invention is a volumetric meteringdevice for the metered delivery of granular and powdery materials,particularly for machines for distributing such materials, comprising ahousing, a metering member supported rotatably in the housing, and afeeler device mounted in the housing and active in the manner of ascraper blade with a lip thereof operative on the metering member. Arestraining mechanism is active on the feeler device in order to keep ita predetermined distance from the metering member. A resilientpreloading mechanism is active on the feeler device in order to pressits operative lip towards the metering member with a predeterminedpreload. Whether it includes a restraining mechanism and a resilientpreloading mechanism or not, the volumetric metering device may bemodified to include an element for altering locally the angle ofintroduction between the feeler device and the metering member; theelement is associated with the feeler device and located immediatelyupstream of the operative lip.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary, but are notrestrictive, of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The characteristics and the advantages of the invention will becomeclearer from the detailed description of a preferred but not exclusiveembodiment described by way of non-limiting example, with reference tothe appended drawings, in which:

FIG. 1 is a schematic view showing, in section, the basic components ofa machine for distributing granular materials;

FIG. 2 is an exploded, perspective view of a delivery device formed inaccordance with the present invention;

FIG. 3 and FIG. 4 are exploded views of respective variants of a detailof the device of FIG. 2;

FIGS. 5, 6, and 7 are perspective views of the device of FIG. 2 in theassembled condition, taken from different angles;

FIGS. 8 and 9 are perspective views of the device of FIG. 2 in an onlypartially assembled condition, taken from different angles;

FIG. 10 is a perspective view of a detail of the device of FIG. 2, on anenlarged scale; and

FIG. 11 is a side view of a further detail of the device of FIG. 2.

PREFERRED EMBODIMENT OF THE INVENTION

With reference to FIG. 1, a machine for distributing granular materials,useful both for sowing seeds and for spreading manure, disinfectants,and the like, is generally indicated by the number 1. The machine 1comprises, basically, one or more hoppers 2 for holding the material tobe spread, a blower 3 which delivers an air-flow under pressure to anair injector 4, a metering device 5 which supplies metered quantities ofthe material present in the hopper into the air-flow generated by theblower 3, and a distributor 6 which distributes the mixed flow of airand material transported thereby towards distribution ducts 7.

The metering device 5 can advantageously be constructed in accordancewith one or more of the teachings of the present invention and is shownin detail in FIG. 2 and the subsequent figures.

The metering device 5 comprises a housing 10 which, by virtue of theprovisions of the invention, can advantageously be constructed in asingle piece (i.e., as one complete, integral, and monolithic unit) bymolding plastic material. The housing 10 comprises a first, upperopening 11 which is open towards the hopper 2; a second, rear opening12, closed in an openable manner by a removable door 14; and an opposed,third opening 15 which admits the granular material to the region of theair injector 4. The housing 10 is closed at the bottom by a feelermember 16 which will be described further below.

The housing 10 further comprises opposed side walls 17 having twocircular and coaxial through-holes 18. The holes 18 serve for housing ametering member, generally indicated 20, in the housing 10.

The metering member 20 comprises a shaft 21 of polygonal, preferablysquare, cross-section, having, at one end, a joint 22 coupling the shaft21 for rotation with a drive shaft (not shown) and, at the other,opposite end, a threaded shank 23 onto which a hand wheel 24 is screwedwith the interposition of a washer 25. The assembly serves to clamp tothe shaft 21 a plurality of metering wheels 26, included in a groupbetween two flanges 27 and intercalated with discs 28.

The flanges 27 are identical to one another and each has two externaltracks 29 a, 29 b which serve to support the metering member 20 in thehousing 10 rotatably but with axial restraint. Support is achieved bythree or more bearings 30 a, 30 b, 30 c, the outer portions of which arein rolling contact with one or other of the tracks 29 a, 29 b. The axialrestraint is not actually necessary for the operation of the devicesince the shaft 21 is itself fixed axially relative to the housing 10 asa result of its connection to the drive shaft by the joint 22. However,to prevent the metering member 20 from accidentally coming out of thehousing 10 when the device is released from the drive shaft, the tracks29 a, 29 b have different diameters (the track 29 a, closer to the sidewall 17 of the housing 10, has a larger diameter) and one bearing 30 ais fixed to the housing 10 removably by the hand wheel 32 and is engagedon the track 29 b so that the shoulder existing between the two tracksperforms the desired axial restraint. In order to remove the meteringmember 20 from the housing 10, the hand wheel 32 is slackened, removingthe bearing 30 a and with it the axial restraint preventing the meteringmember 20 from slipping out.

Both of the flanges 27, or at least one of them, may have a ring ofaxial seats 33 for cores (for examples, screws) cooperating with aproximity detector (not shown) in order to measure the rate of rotationof the metering member 20.

Each metering wheel 26 is molded of plastic material and comprises aplurality of blades 36 which extend radially from a hub 37 having anaxial hole 37 a with a channelled profile. The channels have a profilewhich can be coupled with the shaft 21 and the number of channels is amultiple of the number of sides of the shaft so as to permit differentangular positionings of the wheels 26 on the shaft 21. The wheels 26 canthus be mounted in a manner such that they are offset angularly relativeto one another, improving the uniformity of the output.

Both to take account of this angular offset and to strengthen the blades36, at their free ends, axial appendages 38 are provided on the blades36 and are housed in corresponding holes 39 in the discs 28. The discs28 have circular holes and are not otherwise driven by the shaft 21.

The wheels 26 are interchangeable with second wheels 26 a of differentvolumetric capacity or even with third wheels 40 of low volumetriccapacity, which can also be mounted on the shaft 21 with theinterposition of a release mechanism 41 (see FIGS. 3 and 4). One or moreof the third wheels 40 can thus be disconnected from the drive of theshaft simply by being turned through 180°. In one direction, the releasemechanism 41 in fact brings about driving of the third wheel 40 togetherwith the shaft 21 whereas, in the opposite direction, the releasemechanism 41 is disengaged from the shaft 21, rendering the third wheel40 idle. Moreover, for intermediate capacities, the first and secondwheels 26, 26 a may be combined in the metering member 20 by beingarranged alternately in the group of wheels.

A particular problem which is solved by the invention lies in the factthat some minute seeds with a high oil content (typically rape seeds)tend to release greasy substances into the cells of the metering wheels26 (and into the metering device 5 in general), changing its capacity(to the extent of reducing it to zero). This specific problem has beensolved by the invention by providing a special scraper device 50 whichis mounted downstream of the region in which the seeds fall. The scraper50 comprises a shaft 50 a on which bow-shaped metal scraper members 51,for example, of harmonic steel, are mounted; the number of scrapermembers 51 corresponds to the number of third wheels 40. Each scrapermember 51 has a crosspiece 52 which can follow the profiles of thecells, deforming the corresponding bow resiliently whilst the thirdwheel 40 rotates. The shaft 50 a is in turn rotatable on the housing 10between two positions in which the scraper members 51 are disengagedfrom the wheels or, conversely, are engaged in contact therewith,respectively. Oily residues, which tend to stick to the seeds and to theever-present dust, are thus removed and fall into the pneumaticseed-conveyor duct in order to be removed from the metering device 5.

Again, with oily seeds, in spite of the provision of release mechanisms,one or more of the wheels which are intended to be rendered idle bybeing turned around on the shaft 21 may nevertheless be rotated as aresult of the internal friction which is increased by the presence ofresidues of dirt. To prevent this from occurring, the third wheels 40according to the present invention have, in one or more of the cellsformed in their surfaces between adjacent blades 36, respectivetooth-like formations 54 which, in one direction of rotation, offer thecrosspieces 52 of the scraper members 51 an inclined rear face 55 onwhich the crosspiece 52 does not grip whereas, in the other direction ofrotation, they offer the crosspiece 52 a substantially radial leadingface with which the crosspiece 52 engages, preventing further driving ofthe third wheel 40. An example of this function relates to the centralwheel of FIG. 10.

The ability to release the scrapers 50 from the third wheels 40 whenthey are not required considerably reduces wear of the scrapers 50,maintaining their effective life.

A further advantageous aspect of the invention lies in the structure andfunctional capacity of the feeler member 16. In known solutions, thismember is generally constituted by a pivoting scraper blade providedwith a resilient rubber lip. The main disadvantages resulting from thisstructure are connected with the fact that, with variations in the rateof rotation of the metering member 20, the rubber lip deforms, varyingthe flow-rate of the metering device 5 in a non-predetermined manner.Moreover, the passage of any foreign body (a stone or the like) canblock its pivoting in the open position, with a consequent unexpectedchange in the metering.

The feeler member 16 according to the invention comprises a plurality ofindividual feeler elements 60, each having a first end engaged on ashaft 61 and each carrying, at its opposite end, a fork 62 which housesa further shaft 63 with predetermined clearance. (By “predetermined” ismeant a clearance that is chosen, determined, or known beforehand or inadvance of operation.) The fork prong 66 facing the metering member 20carries a resilient lip 67. Both of the shafts 61, 63 are supportedbetween the side walls 17 of the housing 10.

The feeler elements 60 are spaced apart by fixed plate-shaped separators68, which are also articulated on the shaft 61 at one end and engage theshaft 63 with their opposite ends, but without the ability to pivotabout the shafts.

In the region of the fork 62, there are resilient preloading mechanisms,each including a helical spring 64 and a respective stay 65, which urgethe respective feeler element 60 towards the corresponding meteringwheel. However, the feeler element 60 is kept spaced therefrom by theinteraction of the corresponding prong 66 of the fork 62 with the shaft63. Alternatively, similar resilient preloading mechanisms are arrangedto be active at the opposite end of each feeler element 60. It is thuspossible to apply to the feeler elements 60 a predetermined resilientpreloading, preferably of the order of about 1.5 kg, without thisleading to compression of the lip 67 against the metering member 20which, in conventional systems, is a potential cause of rupture of theseeds distributed. On the other hand, the feeler elements 60 can performoscillations about the shaft 61 which are limited by the other prong ofthe fork 62 so as to prevent the feeler member 16 from openingcompletely, significantly altering the distribution parameters. Thisprecaution is augmented by the provision of individual and independentfeeler elements 60 for each wheel.

With these mechanisms for limiting the pivoting of the feeler member 16,breakages of the feeler elements 60 could occur should foreign bodies ofdimensions larger than the maximum opening between the feeler elements60 and the respective wheels pass through the metering member 20. Toprevent this, according to a further characteristic of the invention,each separator 68 is arranged to have a nib 69 of a shape and size suchas to alter the angle of introduction between the feeler elements 60 andthe metering member 20 so that foreign bodies arriving in theintroduction opening between the feeler elements 60 and the meteringmember 20 are “rejected” by virtue of the increased amplitude of theangle of introduction as defined above and are prevented from enteringthe introduction opening. By way of indication, the angle ofintroduction as varied by the provision of the nibs 69 is about 80°.

According to a further characteristic of the invention, a flow separator70 may be arranged in the region of the third opening 15 for admittingthe granular material into the air-flow which is responsible for itstransportation. The flow separator 70 is of the type comprising a fixedplate supported, by notches 71, on shafts 72, 73 extending between theside walls 17 of the housing 10. The shaft 72 also supports respectivesurfaces for collecting the seed and sending it to the air injector 4.

On the side facing the metering member 20, the flow separator 70 is aplate with an arcuate profile 74 complementary with the outer surface ofa toothless wheel 75 which is fitted centrally between the meteringwheels 26. It is thus possible, with a single metering device 5, tosupply two distributors 6 and respective blowers 3 separately, in factdoubling the capacity of the machine 1.

According to an additional characteristic of the invention, a secondseparator 76 may be disposed in the housing 10, upstream of the meteringmember 20, so as to separate, not only at the output but also at theinput, products which may optionally be different and which can bemetered by a single metering device 5. The second separator 76 comprisesa fixed plate, also provided with an arcuate profile 77 complementarywith the surface of the toothless wheel 75, and has teeth 78 forengagement on a plate 79 which is equipped with two doors 80 and canreplace the door 14 when this arrangement is selected. Amongst theadvantages conferred by this technical solution is the fact that it ispossible to distribute different products through the right-hand andleft-hand sides of the same metering device 5. For example, it ispossible to construct sowing machines with double seed-loading hoppersand a single metering device 5 suitable, for example, for sowingalternating bands of male and female plants for the production ofselected hybrids. That is, it is possible to distribute differentproducts simultaneously, optionally with different metering, adjustablein dependence on the type of metering wheels 26 used for the right-handand left-hand sides.

Finally, a stirrer 81 is provided, supported rotatably between the sidewalls 17 of the housing 10 and rotated by the joint 22, by a belttransmission 82.

The metering device of the present invention thus achieves the objectsindicated, at the same time offering many advantages over the prior art,amongst which is greater ease of handling during operations to assembleand dismantle the individual components. Although illustrated anddescribed above with reference to certain specific embodiments, thepresent invention is nevertheless not intended to be limited to thedetails shown. Rather, various modifications may be made in the detailswithin the scope and range of equivalents of the claims and withoutdeparting from the spirit of the invention.

1. A volumetric metering device for the metered delivery of granular andpowdery materials, the device adapted for use with a machine fordistributing such materials and comprising: a housing having twojuxtaposed walls interconnected to each other by at least oneinterconnecting member so that the walls are rigidly held in aspaced-apart relationship, the housing being molded of plastic materialand formed in a monolithic, integral, single piece; and a meteringmember supported rotatably in the housing.
 2. The device according toclaim 1 in which the housing has an input and a region including anoutput opening and the device further comprises first flow-separatormeans disposed in the region of the output opening of the housing. 3.The device according to claim 2 in which the first separator meanscomprises a fixed plate supported, by notches, on shafts extendingbetween side walls defined in the housing, the plate having, on the sidefacing the metering member, an arcuate profile complementary with theouter surface of a toothless wheel which is fitted centrally betweenmetering wheels of the metering member.
 4. The device according to claim3 further comprising second separator means disposed in the housingupstream of the metering member so as to separate products, which mayoptionally be different, at the input.
 5. The device according to claim4 in which the second separator means comprises a fixed plate having anarcuate profile complementary with the surface of the toothless wheel.6. A volumetric metering device for the metered delivery of granular andpowdery materials, the device adapted for use with a machine fordistributing such materials and comprising: a housing having juxtaposedopenings each with a dimension; and a metering member having at leastone metering wheel clamped between a pair of flanges, the dimension ofat least one juxtaposed opening of the housing allowing the meteringmember, complete with the at least one metering wheel and the flanges,to pass from and towards the housing, at least one of the flanges beingarranged to close the respective opening when the metering member isfitted in the operative position in the housing, and providing rotatablesupport of the metering member in the housing; wherein the flanges carryperipherally at least two rolling tracks for at least one bearing orwheel, a shoulder being defined between the tracks, and the at least onebearing or wheel being restrained on the housing for the rotatablesupport of the metering member and for the axial restraint thereof viathe shoulder.
 7. The device according to claim 6 in which both of theopenings have dimensions such as to allow the metering member, completewith the at least one wheel and the flanges, to pass from and towardsthe housing, both of the flanges being arranged to close the respectiveopenings when the metering member is fitted in the operative position inthe housing, and providing rotatable support of the metering member inthe housing.
 8. The device according to claim 6 in which at least one ofthe bearings or wheels is removable from the housing to allow themetering member to be moved away from and towards the housing.
 9. Thedevice according to claim 6 in which the at least one metering wheel canbe interchanged, combined, or both interchanged and combined with wheelsof different dimensions.
 10. The device according to claim 6 in whichthe housing has an input and a region including an output opening andthe device further comprises first flow-separator means disposed in theregion of the output opening of the housing.
 11. The device according toclaim 10 in which the first separator means comprises a fixed platesupported, by notches, on shafts extending between side walls defined inthe housing, the plate having, on the side facing the metering member,an arcuate profile complementary with the outer surface of a toothlesswheel which is fitted centrally between metering wheels of the meteringmember.
 12. The device according to claim 11 further comprising secondseparator means disposed in the housing upstream of the metering memberso as to separate products, which may optionally be different, at theinput.
 13. The device according to claim 12 in which the secondseparator means comprises a fixed plate having an arcuate profilecomplementary with the surface of the toothless wheel.
 14. A volumetricmetering device for the metered delivery of granular and powderymaterials, the device adapted for use with a machine for distributingsuch materials and comprising: a metering member including a pluralityof metering wheels which are structurally independent of one another andare interposed in a group between a pair of flanges, and a shaft actingas a tie between the flanges in order to clamp in a group the flangesand the metering wheels interposed between them, to constitute a unitwhich can be handled individually; a housing having an input and aregion including an output opening; and first flow-separator meansdisposed in the region of the output opening of the housing and having afixed plate supported, by notches, on shafts extending between sidewalls defined in the housing, the plate having, on the side facing themetering member, an arcuate profile complementary with the outer surfaceof a toothless wheel which is fitted centrally between the meteringwheels of the metering member.
 15. The device according to claim 14 inwhich the shaft comprises, at one of its ends, a joint for connection toa drive shaft.
 16. The device according to claim 15 in which the shafthas means for clamping the group of flanges and wheels at the end remotefrom the joint, the joint acting as an abutment shoulder for theclamping.
 17. The device according to claim 14 in which the shaft has apolygonal cross-section.
 18. The device according to claim 17 in whicheach of the metering wheels has a hub having a hole of polygonalcross-section configured to be coupled with the polygonal cross-sectionof the shaft.
 19. The device according to claim 18 in which the holes inthe hubs of the metering wheels have channelled profiles configured forcoupling with the profile of the shaft and the number of channels is amultiple of the number of sides of the shaft so as to permit variousangular positionings of the metering wheels on the shaft.
 20. The deviceaccording to claim 14 in which the metering wheels can be interchanged,combined, or both interchanged and combined with wheels of differentdimensions.
 21. The device according to claim 14 further comprisingsecond separator means disposed in the housing upstream of the meteringmember so as to separate products, which may optionally be different, atthe input.
 22. The device according to claim 21 in which the secondseparator means comprises a fixed plate having an arcuate profilecomplementary with the surface of the toothless wheel.
 23. A volumetricmetering device for the metered delivery of granular and powderymaterials, the device adapted for use with a machine for distributingsuch materials and comprising a metering member carrying a plurality ofmetering wheels each having a hub with blades that extend radially fromthe hub and clamped together in a group, the blades having appendageslocated proximate the free ends of the blades to strengthen the bladesand restraining the blades of one wheel on the blades of the adjacentwheel.
 24. The device according to claim 23 further comprising a dischaving holes for the appendages, the disc being interposed betweenadjacent metering wheels and constituting an interconnection elementbetween the blades of adjacent wheels.
 25. The device according to claim24 in which the disc has seats for the appendages, the seats beingoffset relative to one another to permit an angularly offsetinterconnection of the sets of blades of adjacent wheels.
 26. The deviceaccording to claim 23 in which the metering wheels can be interchanged,combined, or both interchanged and combined with wheels of differentdimensions.
 27. The device according to claim 23 further comprising ahousing having an input and a region including an output opening, andfirst flow-separator means disposed in the region of the output openingof the housing.
 28. The device according to claim 27 in which the firstseparator means comprises a fixed plate supported, by notches, on shaftsextending between side walls defined in the housing, the plate having,on the side facing the metering member, an arcuate profile complementarywith the outer surface of a toothless wheel which is fitted centrallybetween the metering wheels of the metering member.
 29. The deviceaccording to claim 28 further comprising second separator means disposedin the housing upstream of the metering member so as to separateproducts, which may optionally be different, at the input.
 30. Thedevice according to claim 29 in which the second separator meanscomprises a fixed plate having an arcuate profile complementary with thesurface of the toothless wheel.
 31. A volumetric metering device for themetered delivery of granular and powdery materials, the device adaptedfor use with a machine-s for distributing such materials and comprisinga metering member having metering wheels clamped in a group and keyed toa common drive-transmission shaft, and selective drive-transmissionmeans interposed between the wheels and the shaft in order to excludethe wheels from driving by the shaft or, conversely, to connect thewheels for driving by the shaft, wherein the metering wheels are mountedreversibly on the shaft and the selective drive-transmission meanscomprises a release mechanism which brings about the driving connectionbetween wheels and shaft in a first mounting condition and disconnectionbetween wheels and shaft in a second mounting condition, in which themetering wheels are turned through 180° relative to the first mountingcondition.
 32. The device according to claim 31 further comprising ascraper active on the wheels individually to remove deposits therefrom.33. The device according to claim 32 in which the scraper comprises aplurality of resilient bows each active on the respective wheelindividually.
 34. The device according to claim 32 in which the scraperis movable relative to the metering member between an operative positionin which the scraper is active on the wheels and an inoperative positionin which the scraper is spaced therefrom.
 35. The device according toclaim 32 in which the scraper and the metering wheels comprise a mutualengagement means for restraining the metering wheels in a stationaryposition when they are excluded from driving by the shaft.
 36. Thedevice according to claim 35 in which the mutual engagement meanscomprises a crosspiece on each scraper and at least one tooth-likeelement on each metering wheel, the tooth-like element defining aleading face engaging the crosspiece when the metering wheel is orientedin the second mounting condition and defining an inclined rear facewhich slides relative to the crosspiece when the metering wheel isoriented in the first mounting condition.
 37. A volumetric meteringdevice for the metered delivery of granular and powdery materials, thedevice adapted for use with a machine for distributing such materialsand comprising: a housing; a metering member supported rotatably in thehousing; a feeler device mounted in the housing and active in the mannerof a scraper blade with a lip thereof operative on the metering member;restraining means active on the feeler device for maintaining apredetermined distance between the feeler device and the meteringmember; and a resilient preloading mechanism active on the feeler devicein order to press its operative lip towards the metering member withpredetermined preloading.
 38. The device according to claim 37 in whichthe feeler device comprises a plurality of feeler elements activeindividually and independently on respective corresponding meteringwheels of the metering member.
 39. The device according to claim 38 inwhich the feeler elements are articulated pivotably by their respectiveends remote from the operative lip on a shaft fixed to the housing, andmeans are provided for limiting their pivoting relative to the shaft.40. The device according to claim 39 in which the means for limitingpivoting comprises, at the end corresponding to the operative lip, afork-shaped element between the prongs of which a second shaft is housedwith predetermined clearance.
 41. The device according to claim 37 inwhich the housing has an input and a region including an output openingand the device further comprises first flow-separator means disposed inthe region of the output opening of the housing.
 42. The deviceaccording to claim 41 in which the first separator means comprises afixed plate supported, by notches, on shafts extending between sidewalls defined in the housing, the plate having, on the side facing themetering member, an arcuate profile complementary with the outer surfaceof a toothless wheel which is fitted centrally between metering wheelsof the metering member.
 43. The device according to claim 42 furthercomprising second separator means disposed in the housing upstream ofthe metering member so as to separate products, which may optionally bedifferent, at the input.
 44. The device according to claim 43 in whichthe second separator means comprises a fixed plate having an arcuateprofile complementary with the surface of the toothless wheel.
 45. Avolumetric metering device for the metered delivery of granular andpowdery materials, the device adapted for use with a machine fordistributing such materials and comprising a housing; a metering membersupported rotatably in the housing; a feeler device mounted in thehousing and active in the manner of a scraper blade with a lip thereofoperative on the metering member, the feeler device having a pluralityof feeler elements active individually and independently on respectivecorresponding metering wheels; and means for altering locally the angleof introduction between the feeler device and the metering member, themeans being associated with the feeler device, immediately upstream ofthe operative lip, and including a plurality of separators interposedbetween the feeler elements and each having a nib projecting towards themetering device.
 46. The device according to claim 45 in which thehousing has an input and a region including an output opening and thedevice further comprises first flow-separator means disposed in theregion of the output opening of the housing.
 47. The device according toclaim 46 in which the first separator means comprises a fixed platesupported, by notches, on shafts extending between side walls defined inthe housing, the plate having, on the side facing the metering member,an arcuate profile complementary with the outer surface of a toothlesswheel which is fitted centrally between the metering wheels.
 48. Thedevice according to claim 47 further comprising second separator meansdisposed in the housing upstream of the metering member so as toseparate products, which may optionally be different, at the input. 49.The device according to claim 48 in which the second separator meanscomprises a fixed plate having an arcuate profile complementary with thesurface of the toothless wheel.
 50. A volumetric metering device for themetered delivery of granular and powdery materials, the device adaptedfor use with a machine for distributing such materials and comprising: ametering member having metering wheels clamped in a group and keyed to acommon drive-transmission shaft, and selective drive-transmission meansinterposed between the wheels and the shaft in order to exclude thewheels from driving by the shaft or, conversely, to connect the wheelsfor driving by the shaft; a housing having an input and a regionincluding an output opening; and first flow-separator means disposed inthe region of the output opening of the housing.
 51. The deviceaccording to claim 50 in which the first separator means comprises afixed plate supported, by notches, on shafts extending between sidewalls defined in the housing, the plate having, on the side facing themetering member, an arcuate profile complementary with the outer surfaceof a toothless wheel which is fitted centrally between the meteringwheels of the metering member.
 52. The device according to claim 51further comprising second separator means disposed in the housingupstream of the metering member so as to separate products, which mayoptionally be different, at the input.
 53. The device according to claim52 in which the second separator means comprises a fixed plate having anarcuate profile complementary with the surface of the toothless wheel.54. A volumetric metering device for the metered delivery of granularand powdery materials, the device adapted for use with a machine fordistributing such materials and comprising a metering member including aplurality of metering wheels which are structurally independent of oneanother and are interposed in a group between a pair of flanges, and ashaft acting as a tie between the flanges in order to clamp in a groupthe flanges and the metering wheels interposed between them, toconstitute a unit which can be handled individually; wherein the shafthas a polygonal cross-section, each of the metering wheels has a hubhaving a hole of polygonal cross-section configured to be coupled withthe polygonal cross-section of the shaft, and the holes in the hubs ofthe metering wheels have channelled profiles configured for couplingwith the profile of the shaft and the number of channels is a multipleof the number of sides of the shaft so as to permit various angularpositionings of the metering wheels on the shaft.